Détail de l'auteur
Auteur Annika Hofgaard |
Documents disponibles écrits par cet auteur (4)
Ajouter le résultat dans votre panier Affiner la recherche Interroger des sources externesSpatiotemporal variation in the relationship between boreal forest productivity proxies and climate data / Clémentine Ols in Dendrochronologia, vol 58 (December 2019)
Titre : Spatiotemporal variation in the relationship between boreal forest productivity proxies and climate data Type de document : Article/Communication Auteurs : Clémentine Ols Année de publication : 2019 Projets : PREREAL / Ali, Ahmed Adam Article en page(s) : n° 125648 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] croissance des arbres
[Termes IGN] données météorologiques
[Termes IGN] données spatiotemporelles
[Termes IGN] écosystème forestier
[Termes IGN] forêt boréale
[Termes IGN] hauteur des arbres
[Termes IGN] Normalized Difference Vegetation Index
[Termes IGN] Norvège
[Termes IGN] Pinus sylvestris
[Termes IGN] productivité
[Termes IGN] puits de carbone
[Termes IGN] série temporelle
[Vedettes matières IGN] Végétation et changement climatiqueRésumé : (auteur) The impacts of climate change on high-latitude forest ecosystems are still uncertain. Divergent forest productivity trends have recently been reported both at the local and regional level challenging the projections of boreal tree growth dynamics. The present study investigated (i) the responses of different forest productivity proxies to monthly climate (temperature and precipitation) through space and time; and (ii) the local coherency between these proxies through time at four high-latitude boreal Scots pine sites (coastal and inland) in Norway. Forest productivity proxies consisted of two proxies representing stem growth dynamics (radial and height growth) and one proxy representing canopy dynamics (cumulative May-to-September Normalized Difference Vegetation Index (NDVI)). Between-proxy and climate-proxy correlations were computed over the 1982–2011 period and over two 15-yr sub-periods. Over the entire period, radial growth significantly correlated with current year July temperature, and height growth and cumulative NDVI significantly correlated with previous and current growing season temperatures. Significant climate responses were quite similar across sites, despite some higher sensitivity to non-growing season climate at inland sites. Significant climate-proxy correlations identified over the entire period were temporarily unstable. Local coherency between proxies was generally insignificant. The spatiotemporal instability in climate-proxy correlations observed for all proxies underlines evolving responses to climate and challenges the modelling of forest productivity. The general lack of local coherency between proxies at our four study sites suggests that forest productivity estimations based on a single proxy should be considered with great caution. The combined use of different forest growth metrics may help circumvent uncertainties in capturing responses of forest productivity to climate variability and improve estimations of carbon sequestration by forest ecosystems. Numéro de notice : A2019-618 Affiliation des auteurs : LIF+Ext (2012-2019) Autre URL associée : vers HAL Thématique : FORET Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.dendro.2019.125648 Date de publication en ligne : 06/11/2019 En ligne : https://doi.org/10.1016/j.dendro.2019.125648 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95346
in Dendrochronologia > vol 58 (December 2019) . - n° 125648[article]
Titre : Non-stationary response of tree growth to climate trends along the Arctic margin Type de document : Article/Communication Auteurs : Annika Hofgaard, Auteur ; Clémentine Ols Année de publication : 2019 Projets : PPS Arctic / Hofgaard, Annika Article en page(s) : pp 434 - 451 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] Arctique
[Termes IGN] croissance des arbres
[Termes IGN] écosystème forestier
[Termes IGN] Pinus sylvestris
[Vedettes matières IGN] Végétation et changement climatiqueRésumé : (auteur) Climate change modulates cold-marginal forest ecosystems through changing growth constraints. Understanding spatiotemporal variations in climate–growth relationships is essential to project forest ecosystem dynamics, and climate–environmental feedbacks. We explored variations in growth and climate–growth relationships, along the Arctic margin in north-western Europe, using Scots pine radial growth chronologies, climate data and links between the geographical origin of dominant air masses and growth-controlling variables. Analyses covered nineteenth century to early twenty-first century, with emphasis on two separate warming periods (early twentieth century, and late twentieth to early twenty-first century) and the intervening cooling period. The analyses revealed spatiotemporally unstable growth responses to climate along the Arctic margin. Spatial growth patterns were most similar during the cooling period. However, climate trends (warming, cooling) were weak drivers of growth-limiting climate variables. Instead, a transition in growth-limiting variables occurred throughout the analysed period. A wide range of growing season and non-growing season climate variables limited growth during the early twentieth century. Thereafter the number of growth-limiting variables progressively decreased. This change was accompanied by a contraction in the spatial correspondence between growth and climate, and by a shift in the geographical origin of dominant air masses. This was particularly emphasized close to the Atlantic during recent warming period. The weak association between growth-limiting variables and climate trends question projections of future ecosystem dynamics based on climate variables identified during specific periods (for example, recent warming period). Such projections may be misleading as the diversity of climate conditions constraining cold-marginal forests will be underestimated. Numéro de notice : A2019-620 Affiliation des auteurs : LIF+Ext (2012-2019) Autre URL associée : vers HAL Thématique : FORET Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10021-018-0279-4 Date de publication en ligne : 31/07/2018 En ligne : https://doi.org/10.1007/s10021-018-0279-4 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95349
in Ecosystems > vol 22 n° 2 (March 2019) . - pp 434 - 451[article]
Titre : Monitoring climate sensitivity shifts in tree-rings of Eastern Boreal North America using model-data comparison : Shifts in tree growth sensivity to climate Type de document : Article/Communication Auteurs : Clémentine Ols Année de publication : 2018 Projets : 3-projet - voir note / Hofgaard, Annika Article en page(s) : pp 1042 - 1057 Note générale : bibliographie
This study was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC Strategic and Discovery Grants), the Nordic Forest Research Cooperation Committee (SNS), the Canadian Forest Service (CFS) and the Research Council of Norway (grant 160022/E50). This work was also supported by a fellowship from the Forest Complexity Modelling program(NSERC Strategic and Discovery Grants).Langues : Anglais (eng) Descripteur : [Termes IGN] Amérique du nord
[Termes IGN] analyse de sensibilité
[Termes IGN] analyse diachronique
[Termes IGN] cerne
[Termes IGN] changement climatique
[Termes IGN] dendrochronologie
[Termes IGN] forêt boréale
[Termes IGN] modèle de croissance végétale
[Termes IGN] Picea mariana
[Vedettes matières IGN] Végétation et changement climatiqueRésumé : (auteur) The growth of high-latitude temperature-limited boreal forest ecosystems is projected to become more constrained by soil water availability with continued warming. The purpose of this study was to document ongoing shifts in tree growth sensitivity to the evolving local climate in unmanaged black spruce (Picea mariana (Miller) B.S.P.) forests of eastern boreal North America (49°N–52°N, 58°W–82°W) using a comparative study of field and modeled data. We investigated growth relationships to climate (gridded monthly data) from observed (50 site tree-ring width chronologies) and simulated growth data (stand-level forest growth model) over 1908–2013. No clear strengthening of moisture control over tree growth in recent decades was detected. Despite climate warming, photosynthesis (main driver of the forest growth model) and xylem production (main driver of radial growth) have remained temperature-limited. Analyses revealed, however, a weakening of the influence of growing season temperature on growth during the mid- to late twentieth century in the observed data, particularly in high-latitude (> 51.5°N) mountainous sites. This shift was absent from simulated data, which resulted in clear model-data desynchronization. Thorough investigations revealed that desynchronization was mostly linked to the quality of climate data, with precipitation data being of particular concern. The scarce network of weather stations over eastern boreal North America (> 51.5°N) affects the accuracy of estimated local climate variability and critically limits our ability to detect climate change effects on high-latitude ecosystems, especially at high altitudinal sites. Climate estimates from remote sensing could help address some of these issues in the future. Numéro de notice : A2018-665 Affiliation des auteurs : LIF+Ext (2012-2019) Autre URL associée : Lien vers HAL Thématique : FORET Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10021-017-0203-3 Date de publication en ligne : 27/11/2017 En ligne : http://dx.doi.org/10.1007/s10021-017-0203-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94254
in Ecosystems > vol 21 n° 5 (August 2018) . - pp 1042 - 1057[article]
Titre : Post-1980 shifts in the sensitivity of boreal tree growth to North Atlantic Ocean dynamics and seasonal climate Type de document : Article/Communication Auteurs : Clémentine Ols Année de publication : 2018 Projets : 3-projet - voir note / Hofgaard, Annika Article en page(s) : pp 1 - 12 Note générale : bibliographie
This study was financed by the Natural Sciences and Engineering Research Council of Canada (NSERC) through the project ‘Naturaldisturbances, forest resilience and forest management: the study case of the northern limit for timber allocation in Quebec in a climate change context’(STPGP 413444-11).Langues : Anglais (eng) Descripteur : [Termes IGN] analyse de sensibilité
[Termes IGN] Atlantique Nord
[Termes IGN] cerne
[Termes IGN] circulation océanique
[Termes IGN] climat froid
[Termes IGN] croissance des arbres
[Termes IGN] dendrochronologie
[Termes IGN] forêt boréale
[Termes IGN] inventaire forestier étranger (données)
[Termes IGN] océanographie dynamique
[Termes IGN] Picea abies
[Termes IGN] Picea mariana
[Termes IGN] puits de carbone
[Termes IGN] Québec (Canada)
[Termes IGN] Suède
[Vedettes matières IGN] Végétation et changement climatiqueRésumé : (auteur) The mid-20th century changes in North Atlantic Ocean dynamics, e.g. slow-down of the Atlantic meridional overturning thermohaline circulation (AMOC), have been considered as early signs of tipping points in the Earth climate system. We hypothesized that these changes have significantly altered boreal forest growth dynamics in northeastern North America (NA) and northern Europe (NE), two areas geographically adjacent to the North Atlantic Ocean. To test our hypothesis, we investigated tree growth responses to seasonal large-scale oceanic and atmospheric indices (the AMOC, North Atlantic Oscillation (NAO), and Arctic Oscillation (AO)) and climate (temperature and precipitation) from 1950 onwards, both at the regional and local levels. We developed a network of 6876 black spruce (NA) and 14437 Norway spruce (NE) tree-ring width series, extracted from forest inventory databases. Analyses revealed post-1980 shifts from insignificant to significant tree growth responses to summer oceanic and atmospheric dynamics both in NA (negative responses to NAO and AO indices) and NE (positive response to NAO and AMOC indices). The strength and sign of these responses varied, however, through space with stronger responses in western and central boreal Quebec and in central and northern boreal Sweden, and across scales with stronger responses at the regional level than at the local level. Emerging post-1980 associations with North Atlantic Ocean dynamics synchronized with stronger tree growth responses to local seasonal climate, particularly to winter temperatures. Our results suggest that ongoing and future anomalies in oceanic and atmospheric dynamics may impact forest growth and carbon sequestration to a greater extent than previously thought. Cross-scale differences in responses to North Atlantic Ocean dynamics highlight complex interplays in the effects of local climate and ocean-atmosphere dynamics on tree growth processes and advocate for the use of different spatial scales in climate-growth research to better understand factors controlling tree growth. Numéro de notice : A2018-662 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.gloplacha.2018.03.006 Date de publication en ligne : 18/03/2018 En ligne : https://doi.org/10.1016/j.gloplacha.2018.03.006 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=93844
in Global and Planetary Change > vol 165 (June 2018) . - pp 1 - 12[article]
